Mechanics play an important role in the growth, development, and adaptation of the skeleton. The skeleton is able to respond and adapt to its mechanical environment because bone tissue is a living cellular material, composed of cells that produce their surrounding matrix. In this P&F project we will examine the influence of known mechanical loading on trabecular bone adaptation in our laboratory. A plunger device is mounted on the distal femur of the rabbit and compressive forces are applied to the underlying bone. After loading, the resulting changes in trabecular bone architecture and bone quality will be determined. Specifically, this study will characterize the trabecular architecture and ultrastructural mineral and organic matrix properties of trabecular bone subjected to a variety of specified cyclic loading parameters including load frequency, load magnitude, and number of load cycles. The objective of the study is to test two hypotheses: 1) The microscopic three-dimensional architecture of trabecular bone is altered as a function of known loading conditions. 2) The mineral and organic matrix characteristics of trabecular bone are altered as a result of functional adaptation under a variety of cyclic loading conditions. Our aim is to acquire an understanding of bone functional adaptation and cellular, bone matrix, and bone mineral responses to load. This understanding may e crucial not only in the treatment of osteoporosis, but also in or management of osteoarthritis.